Web Inspector: Modern IDB: Backend should send events when DBs are created/deleted/updated

[Joseph Pecoraro]

* SUMMARY
Modern IDB: Backend should send events when DBs / ObjectStores are created/deleted

This serves multiple purposes:
  (1) under modern IDB there doesn't exist a way to get a list of all the IDB names (we could create one for Inspector eventually)
  (2) currently when a page opens an IDB, it should show up in the tools but doesn't. An event would solve that.

This primarily solves (2) which is a better user experience (dynamically updating available IDB databases/stores). (1) Should be solved eventually but can be done separately.

[Radar WebKit Bug Importer]

<rdar://problem/24115467>

[Joseph Pecoraro]

A basic set of events could include:

    "events": [
        {
            "name": "databaseOpened",
            "parameters": [
                { "name": "databaseWithObjectStores", "$ref": "DatabaseWithObjectStores", "description": "Database with an array of object stores." }
            ]
        },
        {
            "name": "databaseDeleted",
            "parameters": [
                { "name": "securityOrigin", "type": "string", "description": "Security origin." },
                { "name": "databaseName", "type": "string", "description": "Database name." }
            ]
        },
        {
            "name": "objectStoreCreated",
            "parameters": [
                { "name": "securityOrigin", "type": "string", "description": "Security origin." },
                { "name": "databaseName", "type": "string", "description": "Database name." }            
                { "name": "name", "type": "string", "description": "Object store name." },
            ]
        },
        {
            "name": "objectStoreDeleted",
            "parameters": [
                { "name": "securityOrigin", "type": "string", "description": "Security origin." },
                { "name": "databaseName", "type": "string", "description": "Database name." }            
                { "name": "name", "type": "string", "description": "Object store name." },
            ]
        },
    ]

But it might also be worthwhile now to introduce a "databaseId" for securityOrigin/databaseName pairs.

Other possible improvements:
- Send update event when a Database changes version?
- Send update event when an ObjectStore is modified?

[Joseph Pecoraro]

Since object stores can only be created/deleted/modified in upgrades that simplifies things.

We would not need objectStoreCreated/Delete events, just a databaseOpened (which could also double for updated) and databaseDeleted, at that point the object stores should be solid.

[Joseph Pecoraro]

Even if we did this, we would still want a way for the inspector to get a list of all the open IndexedDBs when the inspector opens... So I think it would still make sense for WebCore provide a way to do that in some way.

[Brady Eidson]

Reversing the blocking relationship here - We don't need this to consider Modern IDB to be complete.